Papaverine in Combination With Radiation Therapy for the Treatment of Locally Advanced Rectal Cancer, DINOMITE Trial

This trial (called DINOMITE) tests whether adding papaverine — a drug that relaxes blood vessel walls and may reduce low-oxygen conditions in tumors — to radiation therapy can improve outcomes for people with locally advanced rectal cancer who want to avoid surgery. **You may be eligible if...** - You are 18 or older with good performance status - You have been diagnosed with rectal adenocarcinoma (confirmed by biopsy) that has not spread to other organs - Your tumor is locally advanced (T3-T4 or involves lymph nodes) - Your tumor is microsatellite stable (MSS) — a specific genetic marker - You want to pursue a non-surgical treatment approach after completing standard intensive chemotherapy and radiation - You are willing to undergo MRI scans, tissue biopsies, and blood and stool collection **You may NOT be eligible if...** - Your tumor has spread to distant organs (metastatic) - Your tumor is MSI-high (a different genetic type) - You have serious heart conditions or cannot tolerate the required procedures Talk to your doctor to see if this trial is right for you.